This invention relates to improved method and apparatus for removing pile distortions in thermoplastic fabric created by heat-setting and/or dyeing.
In the case of pile fabrics, which have been heat set at a high temperature with the pile erect and then dyed at a lower temperature during which the pile is substantially disturbed, as in jet dyeing, it is then desired to have the pile return to its original erect condition. One attempt in solving this problem is the tensionless dryer. In this machine, the pile fabric is fed onto a mesh belt which is then transported through a long heated tunnel where either mechanical action or perpendicular air blasts directed at the belt cause the fabric to undergo rather gentle undulations. The fabric is statically charged by friction with the air or contact with various parts of the dryer. The required processing time results in a drying unit over one hundred feet long with a low fabric line speed. There are quality problems associated with a lack of control over the fabric for such a long distance and well as marks that occur when the fabric strikes the upper section of the tunnel.
Another type of pile conditioning device is the use of a high velocity air jet such as U.S. Pat. No. 4,837,902. In this case, the fabric is heated to the desired temperature and the conditioning is accomplished almost instantaneously by vigorous sawtoothed shaped waves which are small in amplitude, but effective due to high accelerations normal to the fabric surface produced by the wave's small bending radius and high velocity. The disadvantage of this process is direct& contact of the heated fabric with the air stream, which tensions the fabric and can set in distortions in sensitive knit fabrics. Also, this process is less effective with highly permeable fabrics, as the air may not be trapped between the fabric and plate.
Yet another type of device vibrates and charges the pile fabric in the heated condition by contact with pneumatically excited diaphragms. The contact of the fabric with the diaphragms combined with the rapid vibrations induced by the air stream cause the diaphragm to wear out a rate in which replacement can be a daily occurrence.
The present invention solves the above problems in a manner not disclosed in the known prior art.